As for the finale, I definitely don't think it was bad, just unbelievably mediocre. The whole time all I could think about was how the show spent so long building under the guise of Harmon et al, and what his finale would have looked like. You can bet it would have been much better, much more emotionally gripping than that. Grave disappointment.

The renewal... I'll be watching, and I hope it gets better quickly. If not I might have to check out.

So why was Harmon asked back? Harmon mentioned in that tweet that we can thank Joel McHale for his return, which squares with what I've heard from people close to the show: several of the castmembers weren't happy with the season 4 scripts and pushed Sony for Harmon's return. Given that — and given that the ratings actually decreased without Harmon, suggesting that "Community" was never going to resemble a broad-based hit no matter who was in charge — I can see Sony deciding to appease both their stars and the fans, and perhaps enhance the show's afterlife on DVD, streaming, etc.